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496 Mag Ho removal of exhaust manifold check valve???


496 Mag Ho removal of exhaust manifold check valve???

Old 06-12-2016, 07:34 AM
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Default 496 Mag Ho removal of exhaust manifold check valve???

After 2 missed seasons I am in a mad rush to get my boat on the water. Starboard engine finished up and running beautifully with the new hardin stainless pumps. Port manifold on thisnstarboard engine is running 20 degrees warmer. I suspect a clogged or sticking check valve in the bottom of the manifold. Is it okay to remove the ball from these 3 way valves thus turning them into an open "T" . Looking at newer engine diagrams they (mercruiser) eliminated them. Thanks in advance.
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Old 06-13-2016, 09:01 AM
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Don't remove the ball! You will just create a loop in the system where you cycle the same water (or some of the same water) around in circles and this will greatly limit the systems cooling ability.

Either replace the ball and coupling or remove the drain system altogether (which is what I did, but I live in Alabama). And you are right, this is a prime area for corrosion and junk to collect which will limit your water flow.

Now, having said that, the starboard manifold will naturally see more water, and I suspect better cooling, than the port since the port gets its water from the heat exchanger after the water has made it across the exchanger and back whereas the starboard gets water after only one trip across.

Perhaps someone on here could comment whether a 20 degree difference is significant?
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Old 06-13-2016, 12:10 PM
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Its an uneven water flow so one manifold is always going to be hotter and this verifiable by the scan tool as well monitoring EMCT temps thru out (port & starboard readings) . I have never seen them run exactly the same temp ever from brand new to a 1000 hours on them - even with newly maintenance items installed right out of the box.

Heat exchanger end cap gaskets and trash build up in heat exchanger causes extra heat from water flow restrictions. The check valves as well.

Overall water volume / water flow rates thru out the raw water side / impeller water volume outputs all effect the cooling temps as well.
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